# Question Video: Calculating Total Magnifying Power Biology

How can the total magnifying power of a light microscope be calculated?

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### Video Transcript

How can the total magnifying power of a light microscope be calculated? Total magnifying power equals the magnifying power of the eyepiece multiplied by the magnifying power of the objective lens. Total magnifying power equals the magnifying power of the eyepiece divided by the magnifying power of the objective lens. Total magnifying power equals the magnifying power of the eyepiece plus the magnifying power of the objective lens. Or total magnifying power equals the magnifying power of the eyepiece minus the magnifying power of the objective lens.

By looking at our answer options, we can tell that the only difference is in the mathematical sign used in each equation. So let’s remove the answers for now so we can find out what the different terms mean and discover which option is correct.

Let’s start by seeing where the eyepiece and objective lenses are located in this light microscope. This is the eyepiece, which is the part the observer will look through. The eyepiece contains the eyepiece lens, which is the lens closest to the observer’s eye. The objective lens is the one closest to the object being observed. Many light microscopes have multiple objective lenses that can be changed depending on the desired magnification of the object, which, if it is part of a living or once living organism, is called a specimen.

In a light microscope, light travels from a light source up through the specimen and then into the objective lens. It then travels through the eyepiece lens and into the eye of the observer. The two lenses converge the light to form a visible image in the eye, which is larger than the actual specimen being viewed. The degree to which an image produced by a microscope is larger than the specimen itself depends on the total magnifying power of the microscope.

Total magnifying power, or total magnification, can be calculated by taking the magnification of the eyepiece lens being used, which is usually 10 times, and multiplying this value by the magnification of the objective lens, which will differ depending on which of the objective lenses you choose to use. For example, if we were viewing a specimen and using the lowest-power objective lens, 10 times, our total magnifying power would be 10, the magnification of the eyepiece lens, multiplied by 10, the magnification of the objective lens. So the total magnifying power of our microscope, and how much the image of the specimen is enlarged by, is 100 times.

We can therefore tell that the correct option to calculate the total magnifying power of a light microscope is the magnifying power of the eyepiece multiplied by the magnifying power of the objective lens.